Clay Review: Sio-2 Brand

Black Ice Porcelain from Sio-2 According to the manufacturer’s website: “Black Ice is a black porcelain body noted for its beautiful black graphite fired color. It has high plasticity, which makes it ideal for wheel-throwing and modeling. Its formula is very stable and provides a secure firing range between Cone 6 and Cone 7 (oxidizing atmosphere). Suitable for tableware (food-safe), according to ISO 6486. Available in extruded body (moist form). Supplied in a practical 5 kg cylindrical format with double packaging." It was $49.50 for 22lbs.

Black Ice fired to Cone 6

Firing range: Cone 6-7 (2269º-2295ºF) Biscuit: Cone 06 (1855ºF) Drying shrinkage: 5.4% Firing shrinkage at Cone 6: 10.3% Porosity (water absorption) at Cone 6: 0.0%” Ships in 11 lb. box.


***DISCLAIMER: this was just my personal experience. Things vary from person to person. I found that different clays react differently to pressure, moisture level, speed, etc. There are a million factors that can make it feel different for you than for me, so PLEASE TAKE IT WITH A GRAIN OF SALT!***


My thoughts:

  • It was perfect softness out of the bag. I did not need to slam wedge or compress much: I found the best way to wedge clay from this brand (Sio-2) is to “rainbow” into logs, then ram’s head wedge.

  • It is more plastic than Sio-2's white porcelain and red earthenware.

  • It has a rubbery feeling, much like the Kentucky Mudworks Brown Bear clay, but less slick. It is like a porcelain version of Brown Bear, and softens easier than Brown Bear. Because of its ‘rubbery’ quality, it cleans off easily and didn’t stain. There is no grog. Another comparison is porosity for water absorption: Brown Bear had .2% while Black ice had 0%.

  • Can build average height, I had better luck holding the sponge inside to pull walls.

  • Doesn’t get soupy with a lot of water. Refining can be achieved without water. At this stage, friction from fingers are not a problem because of the smoothness of the clay, however, sponges do not work. There is too much drag.

  • Difficulty in creating an even floor. I’ve tried multiple times but I think the plaster bat absorbed moisture from the clay too quickly and stiffened it, making it difficult to work the floor. I don’t have this issue with any other clay; for example, even though the plaster bat absorbs moisture quickly from Standard’s Troy Porcelain, the floor remains soft enough to be workable even 15-20 minutes later. Due to this, I made sure to compress the floor with a rib as early as I could, knowing the Black Ice would stiffen soon.

  • Best if the hole is dropped quickly (As opposed to the MC65 Smooth White Clay WC-609 from Miller Clay, which worked best for me when I drop the hole very, very slowly). I cone, center, and drop the hole quite fast, but when I pull walls I am slow. If pulling walls too fast it will collapse, and this seemed to be the issue with three more people I spoke to who have experienced the same thing.

Under LED light
  • Not the best with ribs. If using ribs, dip the rib in water first. The Brown Bear was very good with ribs.

  • I chose to fire to ^05 rather than the recommended ^06, because after my experience with Brown Bear, 06 is just too low.

  • Fires to ^6 as a warm black. There are tints of eggplant, if you can see in the photo. After reading some forums online, the manufacturer’s have said that the black color is derived from oxides.

Turned chocolate brown under clear glaze

I used Mayco’s ^5-6 Stoneware Clear over

the Black Ice, which turned it a milk-chocolate brown, which wasn't what I was going for...

It looked good with Amaco’s commercial Palladium glaze, developing the best metallic results I’ve seen using Palladium.


Overall, I felt that Kentucky Mudworks Brown Bear had a richer, tighter look after being fired to cone 6. Richer because the Black Ice didn’t really look like a pure black, more like a faded graphite.

Brown Bear’s bare surface had a sheen to it when fired to ^6.

Aneto White Porcelain with marbled Black Ice

Aneto White Porcelain ^6-8

"Aneto is translucent white porcelain body which stands out for its high plasticity, and makes it exceptional for wheel-throwing and modeling. Its formula is very stable and provides a secure firing range between Cone 6 and Cone 8." (Sio-2 website)


Firing range: Cone 6-8 (2269º-2320ºF)

Biscuit: Cone 06 (1855ºF)

Drying shrinkage: 4.0%

Firing shrinkage at Cone 7: 9.8%

Porosity (water absorption) at Cone 7: 0.0%

Not plastic at all. The red and the white were not plastic at all, and even fresh clay cracked easily when doing the coil test (wrapping a coil around your finger to see if it stays elastic and smooth). Felt more grainy than I expected, compared to Elaine’s Crystal Cone Six or Standard’s Troy. Even after the glaze firing, the bare clay has a grainy feel to it. Due to the difficult I had throwing large, I would not repurchase this. However, it took glazes beautifully and did not warp. The white is whitest I have ever seen. The ‘whiteness’ is so pure that even the bisque fires a cool white, whereas other porcelains have a pink tint when bisqued (due to iron and other impurities). Also, NOT translucent. Can clay manufacturers please prove to me that these porcelains are translucent in oxidation because YA GIRL IS TIRED. Anyway, $36 for 22lbs.

PF Red Earthenware ^06-04

PF Red Earthenware bisque fired to cone 4, no glaze

Okay. Fires a red terracotta color. Performs fine, I only tried it for hand building. I wish it was “creamier”, there is a stiffness to the body even without grog. It tended to crack easily at the seams. $15.20 for 11lbs.

Compared to Tuckers Red Majolica ^06-04: Tuckers was super creamy, very plastic, very smooth without grog, and fires to a remarkably bright red-orange. I will write a review for that in the future... I may have found my favorite red clay so stay tuned for my thoughts :)

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